The conclusions of our study (Let et al., 2025), published in the journal Environmental Science and Technology, have occurred independently of our initiative on the official website of the European Commission The article summarizes the main findings of the research and their relevance for EU environmental policy, which is implemented and enforced through the Urban Wastewater Treatment Directive (UWWTD).
This laboratory study demonstrates that a range of pharmaceutically active compounds (PhACs) resistant to the treatment processes in modern wastewater treatment plants can accumulate in aquatic insects and persist across developmental stages, including winged adults. Out of 49 PhACs detected in treated wastewater collected from the outflow of the Prachatice wastewater treatment plant into the Živný stream, 15 compounds were subsequently found in aquatic insects—specifically mayflies and caddisflies—reared in this water under laboratory conditions up to the adult stage over a period of up to three months.
The extent of accumulation depended on species, developmental stage, and the physicochemical properties of individual compounds. Larvae consistently exhibited higher concentrations than adults. However, substances such as sertraline and venlafaxine (both antidepressants with moderate to high toxicity for fish and aquatic invertebrates) persisted at elevated concentrations in adult caddisflies, with substantial variability detected between individual specimens.
Key factors influencing PhAC accumulation in adult aquatic insects were the biodegradation half-life of the compounds and the average bioconcentration factors previously established in model aquatic organisms (parameters freely accessible from chemical pollutant databases). Overall, the results confirm that certain PhACs can bioaccumulate in both aquatic larvae and terrestrial adult stages of aquatic insects, which, among other things, serve as prey for birds and bats. These findings thus support the concept of contaminant transfer from aquatic to terrestrial ecosystems via this biologically mediated pathway.
The publication of our study conclusions on the European Commission website represents a step in disseminating the results of our research to the wider public and decision-makers. In this way, the study contributes to an informed debate on environmental challenges and supports the use of scientific knowledge in shaping future policies.
More detailed information can be found in the original scientific article:
Let, M., Grabicová, K., Balzani, P., Musil, M., Roje, S., and Bláha, M., 2025. Bioaccumulation of Pharmaceutically Active Compounds from Treated Urban Wastewaters in Aquatic Insect Larvae and Aerial Adults. Environ. Sci. Technol., 59, 5293−5305.
Author: Marek Let
